Primitive Archer
Main Discussion Area => Bows => Topic started by: 330bull on May 12, 2008, 06:15:12 pm
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Hello,
Basic Information:
I have just built a hazelnut bow that is ~70# @ 26", 58" ntn. It has zero handshock, shoots exactly where I point it, and it retains reflex just a few hours after I'm done shooting. Putting it bluntly, it's a perfect hunting bow if you ask me and I really don't want to mess with it.
Problem:
When I measure for tiller when braced, the upper limb tiller is ~1/16" of an inch less than the lower limb tiller. Both of these measurements take place 3" above the shelf and 3" below the handle. This may not be that big of a deal since I only shoot with two finger; one above & one below.
Questions:
1. Should I even care about the tiller dimension differences?
2. Does it even matter that the tiller is about equal?
3. I have always "shot" for a weaker upper limb so that it measures ~1/8" more than the lower limb. Is this even right?
Thanks in advance and I know most of you will ask for a full draw pic...I may post one tonight but I'm trying like heck to "feel" the bow rather than critique a bow by what a picture says. That bit me in the butt last time. :-[
Joe
Update: OK I shot this bow about 50x tonight and it's still shooting great! However I can easily see the stiff upper limb and how much harder the lower limb is working. I placed a dark red line where I think I should scrape the upper limb to make for a more balanced tiller. Does everyone agree? Any input is appreciated! Thanks! Joe Ps. As of right now this is ~63# @ 26".
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First thing is maybe your not measuring right, if you find center of the bow and measure 6" above and 6" below do you still have positive tiller? Measuring from the shelf and from the handle are not the same if your shelf is 1 1/4" above center like most bows.
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Joe- I think you should leave it alone, too much pos. tiller usually results in too much hand shock. If it's shooting good leave it. I think that the idea of the pos/ neg tiller at brace dosn't matter nearly as much on wood bows as glass bows. Wood bows have so many irregularities that you don't find with glass bows. If the tiller looks good when drawing I saw that's what counts.
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Are the limbs the same length?
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Upper Limb = 29" and measures xxx ~ 3" above the shelf
Lower Limb = 27" and measure xxx+.060" 3" below the bottom of the handle.
See attached pic and thanks for everyone's help!
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If the limbs are different length it changes everything. If it shoots good do NOT mess with it. Justin
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I use asymetrical limbs like you and prefer 1/4" positive tiller on the top limb (at least that's what John Strunk taught me). Since there is more strain on the lower limb I like it to be a little more stiff. I don't know if it is really necessary, but if you're at 70# it seems you have plently of reserve to make a correction if you want. You'd probably only lose a few pounds at most. I generally break in my bows before I make final tiller adjustments. You may want to do that because it could either get worse, better, or stay the same after you put about 500 arrows through it.
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Great advice by everyone. I like the idea of shooting a bunch of arrows before I do anything hasty... :-[ This was the first bow I have ever made that has required such little, if not any, tiller adjustments.
After 50 arrows yesterday the tiller has not changed at all.
Thanks again for everyone's support and I'll post full draw pics tonight for tiller critique.
Joe
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Holy Schematic ;D, That's some computer technical stuff right there. Don't do anything hasty.
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That tells you a lot right there ,if you have shot it 50 shots and nothing has changed that
is a very good thing,must be close to right,like said above it ant glass and can't always
be tillered that way.I prefer 1/4 to 3/8 pos. tiller on the top limb but I usually make mine the same length.Nice work. :)
Pappy
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I think it looks pretty good Joe, I don't like to over analyze bow making, I just have fun, I aim for a decent tiller but don't get to carried away with
the technical stuff. After 50 shots I say any real obvious flaws would have shown up. If your at weight and the bow shot good why mess with it? If the
top limb is stif a few scrapes and I'd say your there, finish it and enjoy.
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Hey Joe, 60 thou (only 1.5mm for us Yurrupeans) is nothing in tillering, as far as I know. I think you can over-analyse this kind of thing ;)
//bob